I change the climate units in my 93 civic. I put it back, but missing one plug dont know where it goes. I put the blue main plug behind the climate in, and there a gray color plug next to it i dont know where it goes. It has 5 wire coming from the blue plug in the middle of climate. Does anyone know where this go?

It not clock, not rear defrost, not lighter because it currently working.
Thank for the help. Sorry i dont have picture to make things easier.